When the degree of integration of LSI (large scale integrated circuit) increases and the width of a gate electrode of a transistor is miniaturized, in a transistor in which gate electrodes and sources/drains are arranged in a planar manner, the channel length is reduced and it becomes difficult to suppress a leak current between the source/drain.
Hence, an attempt is made to form a channel structure into a three-dimensional structure. As a transistor having the three-dimensional channel structure, mention is made of a recessed channel transistor (RCAT).
In the recessed channel transistor, part of a gate electrode is embedded inside a groove formed on a semiconductor substrate. Then, an insulating layer formed on the inner wall of the groove functions as a gate insulating layer and a region along the groove of the semiconductor substrate constitutes a channel.
By forming a channel structure into a three-dimensional structure as described above, it is possible to miniaturize the width of the gate electrode while ensuring the channel length in such a degree that a leak current can be suppressed.
Further, in such a three-dimensional structure, the source/drain end is widened, and therefore, it is also possible to increase the amount of an electric current flowing through the channel.